Alloy



able.

Patented Dec. 20, 1938 UNITED STATES ALLOY Arthur W. Peterson, North Attleboro, Mass., assignor to Metals & Controls Corporation, Attleboro, Mass., a corporation of Massachusetts No Drawing. Application February 23, 1938, Serial No. 191,971

3 Claims.

This invention relates to alloys, and with regard to certain more specific features, to an alloy suitable for combination with gold for jewelry and like purposes.

Among the several objects of the invention may be noted the provision of a base alloy which, when added to gold forms a gold alloy which may be used to manufacture either so-called solid gold objects or gold-plated objects, which gold alloy will wear longer than other gold alloys of similar carats and colors, when subjected to the wear normally encountered by articles of jewelry that are worn on thehands and wrists, etc., or clothing; the provision of a base alloy which, when added to gold forms a gold alloy which has a fine,

close grain, which fineness and closeness of grain make much easier the manufacture of articles from the gold alloy, and prevent what is known as orange peel (surface roughness caused by abnormally large crystals of metal being set in relief by mechanical working of the metal such as bending and other manufacturing operations) during the manufacture of articles of jewelry from the gold alloy; the provision of a base alloy which, when added to gold forms a gold alloywhich may be usedeither as solid gold or as gold plate which has much greater resistance to tarnish and corrosion encountered in atmospheric conditions and in perspiration acids, etc.;' and the provision of a base alloy which, when added to gold forms a gold alloy which, hardness for hardness, is adapted to higher annealing and solderingtemperatures in the manufacture of jewelryarticles from it than other gold alloys now avail- Other objects will be in part obvious and in part pointed out hereinafter. I

The invention accordingly comprises the elements and combinations of elements, and features of composition, which will be exemplified in the alloys hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the manufacture of plated gold articles of jewelry, one of the difficulties encountered is the provision of a gold plate which will stand up against the abrasion caused by clothing, etc., when the article is being worn. The gold plate on such an article is generally very thin, and the life of a plated gold article is determined to a great extent by the resistance to abrasion of the gold plate itself. It has been possible in the past to provide gold alloys of a given carat which will withstand wear to a greater degree than alloys commonly in use. This is ordinarily done by adding to the gold alloy metals of harder nature in considerable amounts. The effect on the alloy is to give it greater hardness, but the resulting color, from the standpoint of the. jewelry industry, is not so good as it was before. Consequently, it has been somewhat of a problem to provide a crystalline appearance on the surface.

hard gold alloy in a given carat which would present a color which, for the given carat of the gold, would be acceptable to the jewelry industry. The alloy which is the subject of this invention provides a metal which when added to gold forms a gold alloy which, for a given carat and given color has much greater wear resistance than other hitherto known gold alloys of similar carat and color. It is known to the applicant, of course, that white gold, which has nickel in it, has superior resistance to tarnish and abrasion than yellow gold of like carat. However, the base al-' loy described herein makes possible the manufacture of a yellow gold alloy whose resistance to wear and corrosion compares favorably with white gold.

In the manufacture of articles of jewelry from gold, it is customary in many cases to use a goldplated stock. In the subsequent bending, stretching, and shaping operations, etc., of the article, the gold plate has a tendency to present a rough This phenomenon is commonly called "orange peel in the jewelry and allied industries. It is a serious defeet and great pains must be taken to prevent it in the manufacture of jewelry items. The present invention discloses an alloy which combines with gold to form a gold alloy having a very fine, close grain which to a great extent prevents this socalled orange peel. This fine, close grain is inherent in the structure, and while fine, close grains can be obtained in other gold alloys, it is only at the expense of much mechanical working. The cobalt (or cobalt and nickel) addition, which is a provision of this invention, prevents abnormal crystal size in the ultimate gold alloy. The present alloy thus provides a metal which, added to gold, affords in either cast, cold-worked or annealed condition a fine, close grain.

Among the many diificulties encountered in the provision of gold alloys for the jewelry industry, is the difiiculty of tarnish and corrosion of the gold by atmospheric conditions and by the acids commonly present in the perspiration of individuals. For example, in the optical goods industry, it is no uncommon occurrence to receive complaints from customers regarding the fact that various parts of their spectacle frames have become eaten away on the surface by the skin acids, with resulting roughness and raggedness of the metal, which in turn causes skin irritation where it comes in contact with the skin. This is caused by the fact that the perspiration acids have eaten away the gold plate which covers a plated spectacle frame. This destruction of the gold plate is a very common occurrence in all gold-plated articles of jewelry which come in contact with the skin of the wearer. One of the solutions in the past has been to substitute a. gold alloy for the plate which has a richer gold content. This is a necessarily expensive procedure and one that it is desired to avoid. The gold alloy which is based on the alloy of the present invention provides a metal which has greater tarnish and corrosion resistance to skin acids, etc., than other known alloys 01' similar carat and color.

In the manufacture of many articles or Jewelry, either the gold-plated variety or the solid carat gold variety, it is necessary many times in the course of manufacture, to submit the article to either high annealing temperatures or highsoldering temperatures. The tendency of hitherto known gold alloys of similar color has been for the alloys to soften unduly with this treatment, creating distortion and too great flexibility in the finished article. For example, in the manufac-.

the hinges soldered on. One difilculty that has been encountered is that the watch case itself 'will buckle due to stresses in the metal being relieved too unevenly. Furthermore, the finished watch case will be so soft that in its use, it is apt to twist and distort in shape,"thus causing misalignment of parts and possible damage to the contained delicate mechanism. Furthermore many gold or gold-plated articles of desirable color for their carat, wear excessively in use. This is caused by softness in the finished article caused by'necessary annealing operations during the manufacturingprocesses. The present invention provides for a gold alloy which is adapted (for given hardness) to higher annealing and soldering temperatures. For .example, ii. the watch case mentioned above were to be annealed at, say, 800 F., it would come out with a certain softness. If the same watch case was made out of the gold alloy obtained from the base alloy 01' this invention, and is subjected to the same annealing temperature, the resulting case will. be harder temper than in the former case. This means, of course, that the metal has more springiness and consequently more resistance to bending and buckling. It will also wear longer, an important desideratum.

Considering the formulae for the alloy which is the subject of this invention, there are three partsz-(l) the base alloy A, (2) the base alloy B, which is the particular, subject or this application, and (3) the ultimate gold alloy. The base alloy A" is substantially comprised 01:

mixture of cobalt and nickel, to the A alloy in the percentage desired. For example:

Per cent Base A 96 Cobalt 4 136 Then to get the ultimate gold alloy, for example, 10 carat gold, flne gold is added to the "3 alloy.

For example: p t

Gold 41.67

A final gold alloy might have these proportions (for example):

Gold 41.66 Silver 7.50 pp r 38.44 Zine 9.90 Cobalt 2.50

This would be a 10 carat gold or a certain color.

The present invention is particularly concerned with a base alloyror making'a range 01 approximately 8-14 carat gold alloys, and within that range the cobalt (or cobalt plus nickel) content or the gold alloy may properly vary from 0.1 to 5% depending on the carat and color desired on the final gold alloy. It it'is desired to change the color, or one or the other properties of the gold alloy, the cobalt (or cobalt plus nickel) content can be changed over approximately a range or 0.1 to 5% and still result in a good quality gold alloy which will have the advantages claimed herein. This variation of 0.1 to 5% in the cobalt (or cobalt plus nickel) content of the final gold alloy means, of course, that the variation of cobalt (or cobalt plus nickel) in the base alloy will be approximately from 0.l5-7.5% in 8 carat gold up to 0.24-12% in 14 carat gold. In varying the cobalt (or cobalt plus nickel) content of the base alloy to produce certain results in the final gold alloy, it is to be noted that as the percentage amount of cobalt (or cobalt plus nickel) increases or decreases, the percentage amount of the base alloy A (silver, copper, and zinc) in the base alloy-3" decreases or increases in like amount respectively. Thus, for a gold of a fixed carat, it is possible to vary the cobalt (or cobalt plus nickel) content to obtain certain final efiects and at the same time keep the carat of the gold constant.

The cobalt or cobalt plus nickel addition should not exceed 5%.of the final gold alloy.

That is, it can be any combination desired or cobalt and nickel (forcertain effects) provided the total of the cobalt plus nickel does not exceed approximately 5% or the final alloy. If greater percentages of either cobalt, or cobalt plus nickel are added, the manufacturing difllculties increase and the final gold alloy may be too hard.

An equation for computing the per cent. amount of cobalt (or cobalt plus nickel) needed in the base alloy "3 to give a desired per cent. of cobalt (or cobalt plus nickel) in the final gold alloy is as follows:

X=Per cent. of cobalt (or cobalt plus nickel) in the base alloy 3". Y=Per cent. of cobalt (or cobalt plus nickel) in the final alloy. Z=Carat of gold desired. Then The efiect or increasing the cobalt (or cobalt plus nickel) content is to produce a paler gold (the decolorlzing eil'ect, or paling efiect of cobalt being roughly only one fourth as great as that oi. nickel), and at the same time to increase its resistance to corrosion, its resistance to wear, and its temper for a given anneal or working operation. It also has a tendency to give the resulting gold alloy a finer, closer grain it the cobalt (or cobalt plus nickel) content is increased. The

eflect on the melting point of the final gold alloy of increase of cobalt and nickel is to raise the melting point.

The ultimate gold alloy herein set forth is claimed in applicant's copending application Serial No. 226,328, filed August 23, 1938.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in carrying out the above compositions without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. An alloy consisting of 0.15% to 12% d a metal selected from the group composed of cobalt and alloys composed of cobalt and nickel, 7% to 18% of silver, 11.4% to 22% of zinc, and the balance copper.

2. An alloy consisting of 0.15% to 12% 01 cobalt, 7% to 18% of silver, 11.4% to 22% of zinc, and the balance copper.

3. An alloy consisting of 0.15% to 12% of an alloy composed of cobalt and nickel, 7% to 18% of silver, 11.4% to 22% of zinc, and the balance copper.

ARTHUR W. PETERSON. 

